Current practice for measuring the amount of surface additive(s) usually consists of a manual technique of sheet disintegration and/or mass balance calculations that are relative in nature.
In the case of starch pickup at the size press, a papermaker (e.g., a boardmaker) will in many cases grossly over apply the amount of starch added to a papermaking process, in order to ensure enough starch is held on the surface of the sheet for the functional intent. Past trials included metering size press applications, which allowed the reduction of starch via a blade application technique. While this allowed a significant reduction of starch in the range of 50-70%, the risk associated with failures due to unpredicted and uncontrolled variations of starch pickup was too great to overcome. As a result, many papermakers reverted to puddle style size presses in order to ensure enough starch was added to the sheet.
Fluorescence has been employed to measure starch concentrations in the papermaking process, but fluorescence alone can lead to inaccurate or imprecise measurements. A more accurate, precise, and timely measurement of the amount of surface additives on a sheet is therefore desired. This potentially will allow the papermaker to drive addition rates to very low levels, while being able to quickly predict and control statistically out of specification addition rates. Even more desirable is a method that provides for the more accurate and timely measurement of surface additives on a sheet that takes into account flutter amplitude and/or sheet temperature. And even more desirable, the method would additionally measure the ratio of tracer to starch in the surface additive.